There appears to be a defect with the shutter curtain opening too far on one side, allowing dust and oil to enter, and stick to a "charged sensor." Perhaps if one used a sealed lens such as the 24-70, exclusively, there would not be a dust issue. But it appears, there would still be an oil issue, which is even worse. Dust is not that hard to "map out." Oil on the other hand is another story.

If such a large gap is present on all D600s experiencing this problem, it's not an issue that will simply go away in time. It will have to be repaired by Nikon.

Who knows if this is what's taking place on all D600s. But LensRentals.com is a highly reputable company. If it's taking place on all 20 of their cameras, in addition to all the complaints that have popped up during the last several weeks, it's likely the culprit has been found.

Since it appears the D800 focal issue has been fixed on D800s that most retailers now have in stock I'd spend the extra $900.00 and save the hassle. It's more money, but there is nothing more frustrating than dealing with Nikon's tech support at the moment.